WASHINGTON, March 28 (Xinhua) -- Russian President Vladimir Putin on Friday called President Barack Obama to discuss a U.S. proposal for a diplomatic resolution to the crisis in Ukraine, the White House said.

Obama suggested Russia put "a concrete response in writing" and the two leaders agreed that U.S. Secretary of State John Kerry and his Russian counterpart Sergei Lavrov would meet to discuss next steps, the White House said in a readout of the phone talks.

Kerry presented Washington's proposal again to Lavrov earlier this week when they met in The Hague on the sidelines of a nuclear summit in the Dutch city.

Obama urged Putin to support the constitutional reform and elections underway in Ukraine and "avoid further provocations," including the buildup of forces on its border with Ukraine.

The American leader also voiced continued U.S. support for "a diplomatic path" in close consultation with the Ukrainian government with a view to de-escalating the crisis.

Obama "made clear that this remains possible only if Russia pulls back its troops and does not take any steps to further violate Ukraine's territorial integrity and sovereignty," the White House said.

He reiterated Washington's strong opposition to the actions already taken by Russia to "violate Ukraine's sovereignty and territorial integrity."

On March 21, Putin signed into law the treaty formally making Crimea part of Russia, five days after the autonomous region of Ukraine voted overwhelmingly in favor of joining Russia in a referendum.

Russia's next move is a top concern of the West, though Moscow said it had no intention to split Ukraine. But Russia also spoke of its responsibility to protect Russian speakers in eastern Ukraine from attacks.

Speaking on CBS's "This Morning" program Friday, Obama urged Russia to pull back troops from the border with Ukraine and start direct talks with its neighbor, as U.S. intelligence agencies have reportedly cited "mounting evidence" about Moscow's possible invasion of eastern Ukraine.

Earlier this week, Russia dismissed reports that it was mobilizing troops to its border with Ukraine.

The Ukrainian crisis dominated Obama's agenda during his trip to Europe this week, in which he had threatened tougher economic sanctions in response to Russia's next move in Ukraine, including targeting its energy and other key sectors.

MOSCOW, March 28 (Xinhua) -- Russian President Vladimir Putin on Friday submitted to the State Duma, lower house of parliament, a proposal to terminate agreements with Ukraine over the Black Sea Fleet.

"Following the signing of the treaty between Russia and Crimea on March 18, 2014 on Crimea's accession to Russia and formation of two new regions within Russia, the essence of the Russian-Ukrainian agreements was lost due to the virtual cessation of legal relations of Russia renting facilities for its Black Sea Fleet in Ukraine," the Kremlin said in a statement. Full story

VIENNA, March 28 (Xinhua) -- President of the Austrian Economic Chambers Christoph Leitl has joined other Austrian business leaders in opposing sanctions against Russia, saying such measures would also harm those who impose them.

Leitl told the Austria Press Agency in an interview Friday that the economy should not be misused in continuing the conflict, but should rather be used as a form of connection. Full story

KIEV, March 28 (Xinhua) -- The Ukrainian Foreign Ministry on Friday hailed a UN resolution affirming the international community's commitment to the country's territorial integrity.

"The resolution reaffirms the sovereignty and territorial integrity of Ukraine within its internationally recognized borders and rebuffs any illegal attempts to change the boundaries of Ukraine," the ministry's press service said in a statement. Full story